1. Field of the Invention
The present invention is related to the field of communications. In particular, the present invention is related to a method and apparatus for transmission of data messages using the control channels of existing wireless communication infrastructure.
2. Description of the Related Art
Transmission of application specific data using the Remote Feature Access control request documented in the Telecommunications Industry Association/Electronic Industry association (TIA/EIA)-41 specification, (IS-41 specification), is well known in the art. Aeris Communications, Inc., of San Jose, Calif., and the assignee of the present invention transmits application specific data in a Remote Feature Access control request. The application specific data is encoded in the Dialed Digits field of the Reverse Control Channel (RECC) packet as a Remote Feature Access Control request transmitted by a communicator or a mobile unit. This RECC transmission is termed a MicroBurst™ packet. The MicroBurst™ packet is handled by a serving system (SS) in the same way as any other control channel message originated by a mobile unit.
Using control channels for transmission of application specific data has significant advantages over using the voice channels for such transmissions. The control channels are robust enough to work where voice channels may be unusable. The control channels broadcast at the maximum allowed radio frequency power allowed for the cellular system. Moreover, each word in the transmission is repeated multiple times to ensure that the correct information is received at the cellular switch. Finally, the control channels are normally underutilized, and may be used for transmission of application specific data without significantly impacting the voice cellular system.
The MicroBurst™ packet that is transmitted by the communicator arrives at a central monitoring station via one or more SSs. When the MicroBurst™ packet arrives at a central monitoring station, the central monitoring station extracts the application specific data embedded in the Dialed Digits field. The application specific data is then acted upon in accordance with the application requirements. For example, the acquired application specific data may be transferred to a local computer system for further processing by the application, or the data may be sent to an Applications Service Provider for further processing.
Since there is no requirement for the SS and the central monitoring station to assign a reverse voice channel to the communicator on receipt of the application specific data packet by the central monitoring station, the central monitoring station requests the SS to terminate communications between the communicator and the SS without requiring voice channel access by the communicator. Since the required application specific data is transmitted within the initial control channel data packet, no further interaction between the central monitoring unit and the communicator is necessary.
However, encoding the application data in the Dialed Digits field of the RECC packet as a Remote Feature Access Control request implies that the data begin with a “Reach-Back” character, i.e., an “*”. This limits manufacturers of communicators and mobile units who must ensure that the Reach-Back character is the first character that is transmitted in the dialed digits field of the RECC packet.
Each communicator is allocated at least one Mobile Identification Number (MIN), and in some situations, communicators may be allocated multiple MINs. For example, when data from multiple sensors of an alarm system are transmitted to a communicator, each sensor may be allocated a particular MIN, thereby utilizing multiple MINs for the multiple sensors. Assigning multiple MINs to each communicator utilizes cellular system resources because for a finite number of digits allowed in a MIN, a finite number of digits may be assigned. Also, the length of the Dialed Digits field transmitted by each communicator is limited to 32 digits. What is needed is a method and apparatus to encode application data in a more flexible way, wherein the first character of the Dialed Digits field is not limited to an “*”, wherein multiple events are triggered without the use of multiple MINs, and the length of Dialed Digits field transmitted is not restricted to 32 digits.